Liner for well bores



y 1967 J. J. MCCULLOUGH 3,330,361

LINER FOR WELL BORES Filed Nov. 23, 1.964

FIG- 2 IN VENTOR.

JQSEPH M CflL L 006/9 United States Patent 3,330,361 LWER FOR WELL BORES Joseph J. McCullough, La Habra, Calif assignor to Union Oil Company of California, Los Angeles, Calif, a corporation of California Filed Nov. 23, 1964, Ser. No. 413,099

9 Claims. (Cl. 166227) This invention relates generally to an improved solids separating device for use in well bores, and more particularly to an apertured well liner having a multiplicity of bridging points extending within the apertures.

The entrainment of sand by a fluid withdrawn from an incompetent subterranean formation has long been a problem in the recovery of crude oil, gas and water from such formations, and it is common practice to position strainers, screens or similar solids-separating devices in the Well bore to remove entrained sand from the well fluid, thereby preventing its passage through the well pump and/ or other well equipment. Although such solids-separating devices take a Wide variety of forms having marked structural differences, in essence they consist of a tubular member adapted to be positioned in a well bore and provided with apertures forming lateral flow passages extending through the walls of the tube which are sufiiciently restricted in size to prevent the passage of sand particles therethrough. However, it is very diflicult to construct devices of such nature for satisfactory use in wells where the sand particles entrained in the well fluid are of very small diameter, e.g., 0.05 inch or less.

Accordingly, the principal object of the present invention is to provide an improved device for separating very finely-divided solids from fluids within a well bore.

Another object is to provide a device of such nature which is of simple design and inexpensive to construct.

Other objects will be apparent to those skilled in the art from the description which follows.

I have found that the foregoing objects and their attendant advantages can be realized by utilizing the sand itself to promote the desired separation. More particularly, I have found that said objects can be realized in an apertured well liner in which the walls of the apertures are coated with a multiplicity of inert granular particles so as to provide the walls of the aforesaid lateral flow passages with a roughened surface offering a multiplicity of bridging points for sand particles passing therethrough. When a liner of such construction is first installed in the well bore and fluid production commenced, some sand may pass through the apertures in the wall into the interior of the liner. However, as flow continues the finelydivided sand particles entrained in the fluid will lodge against the projections provided by the aforesaid granular coating, thereby forming sand bridges in the individual flow passages. Once a sand bridge is established, other particles tend to fill the flow passages upstream from the bridge to form a permeable sand plug which acts as an effective filter bed. The pressure exerted upon these particles by the well fluid tends to keep them lodged in the apertures and to maintain the sand bridge intact. Excessive fluid velocities through the apertures are to be avoided, particularly during initial production, as high velocities tend to prevent formation of the sand bridge.

Any inert granular substance capable of promoting bridging of formation sands may be used to coat the walls of the apertures. The size of the apertures and the coating particles should be selected to afford maximum solid separation with the minimum flow restriction. Accordingly, it is important that the liner be sufliciently apertured to accommodate anticipated fluid flow rates. The granular coating particles may be bonded to the walls of the apertures by any means whereby a relatively permanent bond is achieved. One effective means of such bonding employs 3,330,351 Patented July 11, 1967 a resin which can be hardened to form a permanent bond with the metal and with the inert granular material following application thereto.

The device of this invention can best be understood by reference to the drawings, of which:

FIGURE 1 is an elevation view of a typical section of slotted liner for insertion into a well bore.

FIGURE 2 is an enlarged view of a typical slot in the slotted liner of FIGURE 1.

FIGURE 3 is a partial cross-sectional view of the liner of FIGURE 1 taken along the line 1-1 of FIGURE 1.

The liner of this invention is conveniently fabricated from a section of ordinary steel pipe, threaded or otherwise adapted at its upper end to be attached to equipment for placing it in the well bore opposite the producing formation. The diameter of the liner should be as large as can conveniently be installed in the well bore, since several distinct advantages are obtained with larger diameter liners. For instance, the perimeter of the liner is increased as the diameter increases thereby affording more wall area per lineal foot of liner. Thus, more apertures can be accommodated, and the apertures can be more widely spaced, thereby reducing the restriction to fluid flow and causing less loss in structural strength. Also, larger diameter liners have greater internal volume per foot of length, thereby affording more capacity for accumulation of liquids withdrawn from the formation. Of course, the diameter of the liner is limited by the well diameter, or that of the casing through which it must be inserted. The liner is preferably provided with apertures over a length corresponding to the thickness of the producing formation, and is suspended in the well bore with the apertured section adjacent this zone. With particularly thick formations, the liner may be fabricated in sections for more convenient handling.

The aperatures which extend transversely through the liner Wall may be of any convenient shape, e.g., circular, square, etc., but elongated rectangular slots are most frequently employed. A typical liner having rectangular slot apertures is illustrated in FIGURE 1. Referring now to FIGURE 1, the liner comprises tube 1 having a plurality of rectangular vertical slots 2 arranged in rows about the periphery of tube 1 and aligned therein in vertical rows. Slots 2 may be arranged in horizontal rows, as illustrated, or may be staggered. Similarly, the slots may be arranged in vertical rows, as shown, or adjacent horizontal rows can be offset so that the vertical rows are staggered. Alternatively, the slots can be randomly spaced, or spaced according to any other configuration without affecting the effectiveness of the granular particle coating in promoting the formation of sand bridges within the slots.

Although the size of the apertures in the liner wall will depend somewhat on their shape, with the granular solid particle coating of my invention, the extremely small size apertures which would otherwise be required become unnecessary. In the case of rectangular slots, I prefer a slot having a narrow dimension, or width, of between about .05 and about 0.25 inch and a length of between about 1 and about 8 inches. With circular apertures, I prefer a hole diameter of between about 0.10 and about 0.25 inch.

FIGURE 2 is an enlarged elevation View of a single slot 2 in tube 1. The rectangular slot 2 is defined by sidewalls 3 and 4, top wall 5 and bottom wall 6, and constitutes a rectangular shaped flow passage through the linear wall transverse to the axis of tube 1. Walls 3, 4, 5, and 6 are coated with inert granular particles 7 bonded to these surfaces. FIGURE 3 is an enlarged partial crosssectional view taken along the line 1-1 of FIGURE 1 and shows rectangular slots 2 extending through tube 1 and having their sidewalls 3 and 4 coated along their entire depth with inert granular particles 7.

The granular coating material may comprise any solid substance not soluble in the various fluids to which it will be exposed, and which will withstand formation temperatures. Suitable materials include various sands, and small particles of rock, marble, quartz, glass, metal, petroleum coke, wood, and like substances. Although the particular substance selected may have effect on the bridging tendency of incompetent sands, this effect is generally not as significant as the size and shape of the particulate matter selected. Particles having irregular shapes are preferred, although spheroidal particles can be employed. Superior results are obtained with particles having irregular shapes, but substantially similar size, particularly where the size is selected with regard to the dimensions of the apertures. The particle size should be selected so that when deposited on the walls of the apertures, the particle will extend into the aperture a distance of between about and about 40% of the width thereof. Accordingly, with rectangularly slotted liners, the particles should extend into the fiow conduit a distance of between about 10% and about 40% of the slot width. In the case of circular apertures, the particles should extend a distance of between about 10% and about 40% of the diameter thereof. In either case, a particle having a diameter of about /3 of the slot width, or di-v ameter in the case of circular apertures, is especially preferred.

Any convenient method of applying the granular substance to the walls of the apertures may be employed. One suitable method entails coating the walls of the apertures with an adhesive bonding material, depositing the granular particles on the adhesive surface, and hardening the bonding material to form a cohesive bond between the walls of the aperture and the granular particles. The granular particles may be placed on the walls by blowing, dusting, or other convenient means. Another coating technique entails premixing the bonding material and the granular particles, applying this mixture to the surfaces to be coated, and then hardening the bonding material. There is no advantage to be gained by coating the outer surface of the liner with the granular material, the objective being to deposit this material only within the apertures.

Any material capable of forming an adhesive bond between the granular particles and the walls of the aperture may be employed as a bonding agent. Usually the bonding agent is a liquid'capable of polymerization, or hardening, by the action of temperature or a curing agent. Although a wide variety of plastic and resinous material 'are adaptable to this use, epoxy resins are particularly preferred for ease of application and for the strength and durability of the adhesive bond formed thereby. Suitable epoxides include the condensation products of a diglycidyl ether and epichlorohydrin, such as the conventional Bisphenol A type epoxide obtained on the condensation of bis-(4-hydroxyphenyl)-2,2-propane and epichlorohydrin. Other epoxides, also suitable for use in this invention, either alone or in combination with the aforementioned ether condensation polymers, are styrene oxide, butadiene dioxide, the monoxide and dioxide of vinyl cyclohexane, 4-epoxy-6-methyl-cyclohexane-carboxylate, and other epoxides obtained by the action of peracetic acid and the like on various unsaturates derived from petroleum or vegetable sources.

The condensation reaction whereby the epoxide resin is formed does not occur spontaneously, i.e., it requires initiation and/or promotion by means of heat and/or a condensation catalyst or curing agent. The selection of a curing agent depends upon the particular epoxide to be treated and are generally well known in the epoxy resin art. Such curing agents include various primary-secondary aliphatic amines, hydroxy-aliphatic amines, aromatic primary amines, phenolic tertiary amines, acid anhydrides, halogen gases, hydrogen halides and gaseous boron halogen compounds.

Although an embodiment of an apertured liner employing rectangular slots has been particularly described, it is to be understood that my invention is applicable to any liner having a foraminous structure and wherein the foramina form flow conduits through the liner wall. Similarly, my invention is not limited to the pattern of apertures particularly described, but includes any configuration of apertures arranged in any suitable pattern, and includes attachment of the solid particulate matter to the walls of such aperture conduit by any suitable means.

These and other modifications will be apparent to those skilled in the art from the description contained herein and the claims which follow. 3

I claim:

1. A well bore liner comprising a tubular member hav ing a plurality of apertures through the tube wall, the interior peripheral surfaces of said apertures having particles of an inert granular substance bonded thereto, said particles projecting outwardly into the aperture sufficiently to form a fluid permeable barrier therein.

2. A liner as defined by claim 1 wherein the surface of said peripheral walls of said aperture are substantially covered by said inert granular particles bonded thereto.

3. A liner as defined by claim 1 wherein said inert granular particles extend outwardly from said walls of said aperture into said aperture a distance of between about 10 and about 40 percent of the shortest cross-sectional dimension of said aperture.

4. A liner as defined by claim 1 wherein said inert granular particles are bonded to said walls of said aperture with a resinous bonding agent applied thereto.

5. A liner as defined by claim 1 wherein said inert granular particles are selected from the group consisting of small particles of rock, marble, quartz, glass, metal, petroleum coke, wood and sand.

6. A liner as defined by claim 1 wherein said apertures are rectangular in cross-section.

7. A liner as defined by claim 1 wherein said apertures are circular in cross-section.

8. A liner for well bores penetrating a subterranean formation comprising: an elongated tube having an internal axial flow conduit enclosed by a tube wall, said tube being circular in cross-section and having an outside diameter only slightly smaller than the diameter of said well bore;

a plurality of elongated rectangular apertures in said tube wall communicating from the exterior of said tube wall to said internal axial flow conduit;

a plurality of inert solid particles substantially covering the peripheral surface of said apertures through said tube walls selected from the group consisting essentially of rock, marble, qjuartz, glass, metal, petroleum coke, wood and sand bonded to said surface by a resinous bonding agent applied thereto, said particles projecting outwardly from said surface into said apertures a distance of between about 10 and about 40 percent of the width of said apertures. V

9. The liner of claim 8 wherein said resinous bonding agent is an epoxy resin.

References Cited UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner. D. H. BROWN, Assistant Examiner. 

1. A WELL BORE LINER COMPRISING A TUBULAR MEMBER HAVING A PLURALITY OF APERTURES THROUGH THE TUBE WALL, THE INTERIOR PERIPHERAL SURFACES OF SAID APERTURES HAVING PARTICLES OF AN INERT GRANULAR SUBSTANCE BONDED THERETO, SAID PARTICLES PROJECTING OUTWARDLY INTO THE APERTURE SUFFICIENTLY TO FORM A FLUID PERMEABLE BARRIER THEREIN. 